This invention relates to a method and apparatus for plating a strip.
Several applications presently exist for flexible, insulating material coated with a metal. Chief among them are the contact fingers in Tape Automated Bonding (TAB), and flexible circuits such as those used in certain connectors (see U.S. Pat. No. 4,806,107 issued to Arnold et al) and in laminated printed circuit boards. In many such applications, the insulating material is processed in the form of a wide (typically 14 inches) continuous strip. Difficulties have been encountered in providing a uniform coating on such a wide strip. Further, in most applications, it is desirable to produce a coated strip which has an elongation of at least 10 percent.
It is generally known to plate a printed circuit board with copper by means of a copper sulfate bath, and elongations up to 23 percent have been reported (see, e.g., U.S. Pat. No. 4,242,181 issued to Malak). Electroforming processes have also been described involving high current densities, agitation of the bath, and achievement of elongation of 12-14 percent (see U.S. Pat. No. 4,781,799 issued to Herbert, Jr. et al). Finally, it is generally known to form a foaming electrolyte by pumping a gas therein (see, U.S. Pat. No. 4,360,410 issued to Fletcher et al).
It does not appear, however, that anyone has previously taught how to consistently achieve a uniform coating of a wide insulating strip with high elongation.